The present invention is directed to a pollutant treating device for removing pollutants from a gas, especially ambient air flowing naturally through the engine compartment of a motor vehicle. The device contains a pollutant treating component including a catalyst and/or an adsorbent. The present invention is especially adapted to a renewable pollutant treating device used in automobiles which can be readily replaced and/or reused.
The removal of pollutants from a gas (e.g. air) requires that the gas moves in proximity to a material that can either chemically convert the pollutants to non-toxic materials and/or absorb the pollutants so that the gas may be cleansed. In order to provide conditions for the removal of pollutants from gases, it is necessary to have a flow of air and in some cases a source of heat to elevate the temperature of the gas flow to above a critical temperature particularly when using catalysts to promote chemical conversion of the pollutants.
Such devices employ catalytic materials to convert pollutants to non-toxic materials. Such catalysts include noble metal catalysts (e.g. platinum, rhodium and the like) as well as the less expensive base metal catalysts such as copper, iron, manganese and the like.
Systems employing catalysts for the removal of pollutants from gasoline and diesel exhaust are commonplace in the auto industry. Catalytic converters are devices which contain a catalytic material to promote the chemical conversion of such pollutants including hydrocarbons, sulfur compounds and nitrogen compounds to produce non-toxic gases such as carbon dioxide, water vapor and the like. Catalytic converters of the type employed in the automotive industry to treat engine exhaust are expensive and not readily replaceable. Currently, the EPA does not permit individuals to remove catalytic converters from motor vehicles. They are typically provided with relatively high concentrations of very expensive catalysts so that replacement over the life of the automobile is preferably not necessary.
It is also known in the art to use adsorbents to entrap pollutants within a maze of interstitial spaces while allowing air to pass therethrough. Examples of such adsorbents include activated carbon, silica, zeolites and the like.
While catalytic converters in automobiles are used to treat exhaust, there are generally no provisions for treating ambient air to remove pollutants such as hydrocarbons, carbon monoxide and ozone contained therein. Such devices would have to be inexpensive compared to typical catalytic converters. Accordingly, the devices would have to employ generally less expensive catalytic materials and/or adsorbents and be readily replaceable and/or reusable.
It has been disclosed to treat atmospheric air directed into a confined space to remove undesirable components in the air. However, there has been little effort to treat pollutants which are already in the environment; the environment has been left to its own self cleansing systems. References are known which disclose proactively cleaning the environment. U.S. Pat. No. 3,738,088 discloses an air filtering assembly for cleaning pollution from the ambient air by utilizing a vehicle as a mobile cleaning device. A variety of elements are disclosed to be used in combination with a vehicle to clean the ambient air as the vehicle is driven through the environment. In particular, there is disclosed ducting to control air stream velocity and direct the air to various filter means. The filter means can include filters and electronic precipitators. Catalyzed postfilters are disclosed to be useful to treat nonparticulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxide and/or sulfur oxides, and the like.
Another such reference is German Patent DE 43 18 738 which discloses using a motor vehicle as a carrier for conventional filters and/or catalysts to physically and chemically clean outside air.
Another approach is disclosed in U.S. Pat. No. 5,147,429. There is disclosed a mobile airborne air cleaning station. In particular this patent features a dirigible for collecting air. The dirigible has a plurality of different types of air cleaning devices contained therein. The air cleaning devices disclosed include wet scrubbers, filtration machines, and cyclonic spray scrubbers.
The difficulty with devices disclosed to proactively clean the atmospheric air is that they require new and additional equipment. Even the modified vehicle disclosed in U.S. Pat. No. 3,738,088 requires ducting and filters which can include catalytic filters.
DE 40 07 965 C2 to Klaus Hager discloses a catalyst comprising copper oxides for converting ozone and a mixture of copper oxides and manganese oxides for converting carbon monoxide. The catalyst can be applied as a coating to a self heating radiator, oil coolers or charged-air coolers. The catalyst coating comprises heat resistant binders which are also gas permeable. It is indicated that the copper oxides and manganese oxides are widely used in gas mask filters and have the disadvantage of being poisoned by water vapor. However, the heating of the surfaces of the automobile during operation evaporates the water. In this way, continuous use of the catalyst is possible since no drying agent is necessary.
It would therefore be a significant advance in the art of removing pollutants from ambient air flowing through the engine compartment of a motor vehicle to provide a pollutant treating device that can be positioned within the normal flow patterns of the ambient air without the need to employ additional equipment for directing the ambient air flow.
The present invention is generally directed to an apparatus and method to treat the atmosphere. In particular, the present invention provides for the removal of atmospheric pollutants as they travel in normal flow patterns within the engine compartment of a motor vehicle. In accordance with the present invention the pollutants can be treated with a pollutant treating device that is convenient to use, relatively inexpensive and, in a preferred form of the invention, readily renewable. The pollutant treating device can remove pollutants from the atmosphere by catalytically promoting the conversion of the pollutants to harmless by-products and/or by adsorbing the pollutants.
More specifically the present invention is directed to a pollutant treating device positioned in the engine compartment of a motor vehicle which lies in at least one normal flow pattern of ambient air as it passes through the engine compartment. The pollutant treating device comprises at least one pollutant treating component in the form of a structure having a pollutant treating composition. The structure is positioned within a normal flow pattern of ambient air passing through the engine compartment and thereby is in flow communication with pollutants contained within the ambient air. The pollutant treating composition which may include a catalyst and/or an adsorbent converts and/or entraps the pollutants to thereby remove the same from the ambient air. The pollutant free ambient air is then returned to the atmosphere.
In accordance with an important aspect of the present invention the ambient air entering the engine compartment of the motor vehicle is allowed to flow through normal flow patterns within the engine compartment. In particular, there is no special equipment provided to the engine compartment for the purpose of directing the ambient air towards a particular location. Instead, the pollutant treating device of the present invention is positioned in at least one normal flow pattern of the ambient air so that its sole purpose is to enable effective contact between the pollutants and the pollutant treating composition.
In a preferred embodiment of the invention, the pollutant treating device is positioned in proximity to the radiator of the motor vehicle so as to be in flow communication with the ambient air passing into or out of the radiator. The pollutant treating device may also be positioned in proximity to the air conditioner condenser, air charge cooler and/or radiator fan since these engine compartment components are typically in at least one normal flow pattern of the ambient air.
In another preferred embodiment of the invention the pollutant treating device is provided with a support means, such as a bracket assembly which enables the pollutant treating component to be readily renewed (e.g. replaced or reused) when the pollutant treating device can no longer remove pollutants from the ambient air.
As used herein, the term xe2x80x9catmospherexe2x80x9d shall mean the mass of air surrounding the earth. The term xe2x80x9cambient airxe2x80x9d shall mean the atmosphere which is normally flowing through a motor vehicle engine compartment or is drawn or forced towards the pollutant treating device. It is intended to include air which has been heated either incidentally or by a heating means. The device can contain a catalyst composition to convert pollutants into non-toxic materials and/or an adsorbent for adsorbing pollutants to provide at least a substantially pollutant-free gas. Also as used herein the term xe2x80x9ccatalyst compositionxe2x80x9d is intended to mean compositions containing catalytic materials, adsorbents or combinations thereof.
The term xe2x80x9cnormal flow patternxe2x80x9d shall mean the flow path of ambient air through an engine compartment containing only vehicle components which are required for the normal operation of the motor vehicle.
The term xe2x80x9crenewablexe2x80x9d shall mean that the pollutant treating device can be readily replaced or reused for the purpose of removing pollutants from the ambient air. The term xe2x80x9cengine compartmentxe2x80x9d shall be used in its customary broad sense to include all components of a motor vehicle contained within the space defined by the grille, the rear fire wall and the side fender wells as well as the underchassis and hood. Examples of motor vehicle components contained within the engine compartment include an air conditioner condenser, a radiator, at least one fan, an engine, an air charge cooler also referred to as an intercooler or aftercooler, fluid containers (for brake fluids, transmission fluids, oils and the like) and the like. The engine compartment includes such components regardless of whether the engine compartment is located in the front, rear or mid-position of the motor vehicle.
The present invention is directed to compositions, methods and articles to treat pollutants in ambient air. Such pollutants may typically comprise from 0 to 400 parts, more typically 1 to 300 parts, and yet more typically 1 to 200 parts, per billion (ppb) ozone; 0 to 30 parts, and more typically 1 to 20 parts, per million (ppm) carbon monoxide; and 2 to 3000 ppb unsaturated hydrocarbon compounds such as C2 to C20 olefins and partially oxygenated hydrocarbons such as alcohols, aldehydes, esters, ethers, ketones and the like. Other pollutants present may include nitrogen oxides and sulfur oxides. The National Ambient Air Quality Standard for ozone is 120 ppb, and carbon monoxide is 9 ppm.
Pollutant treating compositions include catalyst compositions useful for catalyzing the conversion of pollutants present in the atmosphere to non-objectionable materials. Alternatively, adsorption compositions can be used as the pollutant treating composition to adsorb pollutants which can be destroyed upon adsorption, or stored for further treatment at a later time. Such compositions are disclosed in commonly assigned United States patent application entitled xe2x80x9cVehicle having Atmosphere Pollutant Treating Surfacexe2x80x9d, attorney docket no. 3777C filed concurrently herewith and bearing U.S. Ser. No. 08/589,182, which is incorporated herein by reference.
Catalyst compositions can be used which can assist in the conversion of the pollutants to harmless compounds or to less harmful compounds. Useful and preferred catalyst compositions include compositions which catalyze the reaction of ozone to form oxygen, catalyze the reaction of carbon monoxide to form carbon dioxide, and/or catalyze the reaction of hydrocarbons to form water and carbon dioxide. Specific and preferred catalysts to catalyze the reaction of hydrocarbons are useful for catalyzing the reaction of low molecular weight unsaturated hydrocarbons having from two to twenty carbons and at least one double bond, such as C2 to about C8 mono-olefins. Such low molecular weight hydrocarbons have been identified as being sufficiently reactive to cause smog. Particular olefins which can be reacted include propylene and butylene. A useful and preferred catalyst can catalyze the reactions of both ozone and carbon monoxide; and preferably ozone, carbon monoxide and hydrocarbons.
Ozonexe2x80x94Useful and preferred catalyst compositions to treat ozone include a composition comprising manganese compounds including oxides such as Mn2O3 and MnO2 with a preferred composition comprising xcex1-MnO2, and cryptomelane being most preferred. Other useful and preferred compositions include a mixture of MnO2 and CuO. Specific and preferred compositions comprise hopcalite which contains CuO and MnO2 and, more preferably Carulite(copyright) which contains MnO2, CuO and Al2O3 and sold by the Carus Chemical Co. An alternative composition comprises a refractory metal oxide support on which is dispersed a catalytically effective amount of a palladium component and preferably also includes a manganese component. Also useful is a catalyst comprising a precious metal component, preferably a platinum component on a support of coprecipitated zirconia and manganese oxide. The use of this coprecipitated support has been found to be particularly effective to enable a platinum component to be used to treat ozone. Yet another composition which can result in the conversion of ozone to oxygen comprises carbon, and palladium or platinum supported on carbon, manganese dioxide, Carulite(copyright) and/or hopcalite. Manganese supported on a refractory oxide such as alumina has also been found to be useful.
Carbon Monoxidexe2x80x94Useful and preferred catalyst compositions to treat carbon monoxide include a composition comprising a refractory metal oxide support on which is dispersed a catalytically effective amount of a platinum or palladium component, preferably a platinum component. A most preferred catalyst composition to treat carbon monoxide comprises a reduced platinum group component supported on a refractory metal oxide, preferably titania. Useful catalytic materials include precious metal components including platinum group components which include the metals and their compounds. Such metals can be selected from platinum, palladium, rhodium and ruthenium, gold and/or silver components. Platinum will also result in the catalytic reaction of ozone. Also useful is a catalyst comprising a precious metal component, preferably a platinum component on a support of coprecipitated zirconia and manganese dioxide. Preferably, this catalyst embodiment is reduced. Other useful compositions which can convert carbon monoxide to carbon dioxide include a platinum component supported on carbon or a support comprising manganese dioxide. Preferred catalysts to treat such pollutants are reduced. Another composition useful to treat carbon monoxide comprises a platinum group metal component, preferably a platinum component, a refractory oxide support, preferably alumina and titania and at least one metal component selected from a tungsten component and rhenium component, preferably in the metal oxide form.
Hydrocarbonsxe2x80x94Useful and preferred catalyst compositions to treat unsaturated hydrocarbons including C2 to about C20 olefins and typically C2 to C8 mono-olefins such as propylene and partially oxygenated hydrocarbons as recited have been found to be the same type as recited for use in catalyzing the reaction of carbon monoxide with the preferred compositions for unsaturated hydrocarbons comprising a reduced platinum component and a refractory metal oxide support for the platinum component. A preferred refractory metal oxide support is titania. Other useful compositions which can convert hydrocarbons to carbon dioxide and water include a platinum component supported on carbon or a support comprising manganese dioxide. Preferred catalysts to treat such pollutants are reduced. Another composition useful to convert hydrocarbons comprises a platinum group metal component, preferably a platinum component, a refractory oxide support, preferably alumina and titania and at least one metal component selected from a tungsten component and rhenium component, preferably in the metal oxide form.
Ozone and Carbon Monoxidexe2x80x94A useful and preferred catalyst which can treat both ozone and carbon monoxide comprises a support such as a refractory metal oxide support on which is dispersed a precious metal component. The refractory oxide support can comprise a support component selected from the group consisting of ceria, alumina, silica, titania, zirconia, and mixtures thereof. Also useful as a support for precious metal catalyst components is a coprecipitate of zirconia and manganese oxides. Most preferably, this support is used with a platinum component and the catalyst is in reduced form. This single catalyst has been found to effectively treat both ozone and carbon monoxide. Other useful and preferred precious metal components are comprised of precious metal components selected from palladium and also platinum components with palladium preferred. A combination of a ceria support with a palladium component results in an effective catalyst for treating both ozone and carbon monoxide. Other useful and preferred catalysts to treat both ozone and carbon monoxide include a platinum group component, preferably a platinum component or palladium component and more preferably a platinum component, on titania or on a combination of zirconia and silica. Other useful compositions which can convert ozone to oxygen and carbon monoxide to carbon dioxide include a platinum component supported on carbon or on a support comprising manganese dioxide. Preferred catalysts are reduced.
Ozone, Carbon Monoxide and Hydrocarbonsxe2x80x94A useful and preferred catalyst which can treat ozone, carbon monoxide and hydrocarbons, typically low molecular weight olefins (C2 to about C20) and typically C2 to C8 mono-olefins and partially oxygenated hydrocarbons as recited comprises a support, preferably a refractory metal oxide support on which is dispersed a precious metal component. The refractory metal oxide support can comprise a support component selected from the group consisting of ceria, alumina, titania, zirconia and mixtures thereof with titania most preferred. Useful and preferred precious metal components are comprised of precious metal components selected from platinum group components including palladium and platinum components with platinum most preferred. It has been found that a combination of a titania support with a platinum component results in the most effective catalyst for treating ozone, carbon monoxide and low molecular weight gaseous olefin compounds. It is preferred to reduce the platinum group components with a suitable reducing agent. Other useful compositions which can convert ozone to oxygen, carbon monoxide to carbon dioxide, and hydrocarbons to carbon dioxide include a platinum component supported on carbon, a support comprising manganese dioxide, or a support comprising a coprecipitate of manganese oxides and zirconia. Preferred catalysts are reduced.
The above compositions can be applied by coating to the pollutant treating device. Particularly preferred compositions catalyze the destruction of ozone, carbon monoxide and/or unsaturated low molecular weight olefinic compounds at ambient conditions or ambient operating conditions. Ambient conditions are the conditions of the atmosphere. Ambient operating conditions shall mean the conditions, such as temperature, of the pollutant treating device during normal operation of the vehicle without the use of additional energy directed to heating the pollutant treating device. It has been found that preferred catalysts which catalyze the reaction of ozone can catalyze the reaction of ozone at ambient conditions in ranges as low as 5 to 30xc2x0 C.
Various of the catalyst compositions can be combined, and a combined coating applied to the pollutant treating device. Alternatively, different surfaces or different parts of the same surface of the device can be coated with different catalyst compositions.
The method and apparatus of the present invention are designed so that the pollutants can be treated at ambient atmospheric conditions. The present invention is particularly useful for treating ozone with suitable catalysts useful to destroy such pollutants even at ambient conditions, and at vehicle surface temperatures typically from at least 0xc2x0 C., preferably from 10 to 105xc2x0 C., and more preferably from 40 to 100xc2x0 C. Carbon monoxide is preferably treated at atmosphere contacting surface temperatures from 40 to 105xc2x0 C. Low molecular weight hydrocarbons, typically unsaturated hydrocarbons having at least one unsaturated bond, such as C2 to C20 olefins, and typically C2 to C8 mono-olefins are preferably treated at temperatures of from 40 to 105xc2x0 C. The percent conversion of ozone, carbon monoxide and/or hydrocarbons depends on the temperature and space velocity of the atmospheric air relative to the pollutant treating device.
Accordingly, the present invention, in most preferred embodiments can result in at least reducing the ozone, carbon monoxide and/or hydrocarbon levels present in the atmosphere without the addition of any mechanical features or energy source to existing vehicles, particularly motor vehicles. Additionally, the catalytic reaction takes place at the normal ambient operating conditions so that no changes in the construction or method of operation of the motor vehicle are required.
While the apparatus and method of the present invention are generally directed to treating the atmosphere, it will be appreciated that variations of the apparatus are contemplated for use to treat volumes of air in enclosed spaces. For example, a motor vehicle having a pollutant treating device can be used to treat the air within factories, mines and tunnels. Such apparatus can include vehicles used in such environments.
While the preferred embodiments of the present invention are directed to the destruction of pollutants at the ambient operating temperatures of the atmosphere contacting surface, it is also desirable to treat pollutants which have a catalyzed reaction temperature higher than the ambient temperature or ambient operating temperature of the atmosphere contacting surface. Such pollutants include hydrocarbons and nitrogen oxides and to some extent carbon monoxide. These pollutants can be treated at higher temperatures typically in the range of at least 100 to 450xc2x0 C. This can be accomplished, for example, by the use of an auxiliary heated catalyzed surface. By an auxiliary heated surface, it is meant that there are supplemental means to heat the surface. A preferred auxiliary heated surface is the surface of an electrically heated catalyzed monolith such as an electrically heated catalyzed metal honeycomb of the type known to those skilled in the art. Electricity can be provided by batteries or a generator such as are present in motor vehicles. The catalyst composition can be any well known oxidation and/or reduction catalyst, preferably a three way catalyst (TWC) comprising precious group metals such as platinum, palladium, rhodium and the like supported on refractory oxide supports. An auxiliary heated catalyzed surface can be used in combination with, and preferably downstream of, the pollutant treating device to further treat the pollutants.
As previously stated, adsorption compositions can also be used to adsorb pollutants such as hydrocarbons and/or particulate matter for later oxidation or subsequent removal. Useful and preferred adsorption compositions include zeolites, other molecular sieves, carbon, and Group IIA alkaline earth metal oxides such as calcium oxide. Hydrocarbons and particulate matter can be adsorbed from 0xc2x0 C. to 110xc2x0 C. and subsequently treated by desorption followed by catalytic reaction or incineration.
The renewable device of the present invention can be readily installed, and replaced and/or reused in a motor vehicle, air conditioning unit or other device in which a gas flow (e.g. air flow) is present. The renewable device may generally be placed anywhere in a normal flow pattern of the ambient air passing through the engine compartment of the motor vehicle. It is preferred that the device be placed in proximity to a source of heat (e.g. radiator) so that the temperature of the ambient air may be elevated prior to contacting the device, or that heat be provided by some other means.
The ambient air is drawn into contact with the pollutant treating device by natural wind currents or preferably by the use of an air drawing means such as a fan or the like. By way of example, the fan may be positioned in a tunnel, or as part of an air conditioning system or a fan, preferably in motor vehicles a standard fan, used in a conventional cooling system of a motor vehicle. The fan is typically operated by a power source such as a battery, preferably the conventional 12 volt battery used in a motor vehicle, solar panel and the like.